Application of an Equilibrium Model for an Electrified Fluid Interface—Electrospray Using a PDMS Microfluidic Device

An experimental investigation of an electrified fluid interface is presented. The experimental findings are related to a previously developed analytical model of Gubarenko , which is used to determine when a fluidic interface under electrical stress is in equilibrium, and to observations reported in the literature. The effect of key parameters on causing the interface to rupture, form, and maintain an electrospray is investigated. The experimental results reveal the dependence of interface shape on operational parameters, the impact of the interface apex angle on equilibrium, the conditions that cause either dripping mode or cone-jet mode, and the structure of operational domains. This paper confirms predictions made using the analytical model, including the range of parameters that cause the onset and steadiness of a quasi-equilibrium (electrospray) state of the interface. Testing is performed using an electrospray emitter chip fabricated from two layers of Polydimethylsiloxane and one layer of glass. The model and experimental results assist in design decisions for electrospray emitters. Applications of electrified interfaces (electrosprays) are found in mass spectrometry, microfluidics, material deposition, and colloidal thrusters for propulsion.